Major rewrite of nyaa.js to make the searches use the rss

This lets us compare entries by their seeders and age (which isn't available in a search).
The !nyaa, !nyaan, !nyaall commands no longer return a random entry, but pick one based on number of seeders and age. The current score formula is <number of seeders> - <age in hours> which does okay, but maybe something more biased towards small age would be better. Also, could maybe log the age, so that really old torrents are still in the game?